This heating unit (100) includes a heater (30) that generates heat when supplied with electric power, and at least two switching elements (10, 20) connected in series with the heater 30 and switching between supplying and interrupting of electric power to the heater (30) by being turned on and off. The first switching element (10) of the at least two switching elements (10, 20) remains in the ON state while the second switching element (20) repeatedly switches between the ON and OFF states.